Roadway markers are utilized in a variety of traffic control applications. Many roadway markers are permanently affixed to a roadway to delineate lanes of traffic on the roadway. Other roadway markers are used to temporarily delineate construction or work areas. Roadway markers used in such applications are called temporary roadway markers. Both permanent and temporary roadway markers are attached to a roadway with a suitable adhesive.
Permanent roadway markers remain in place and define traffic lanes, identify obstacles and perform other well known functions. Many permanent roadway markers are raised to create a rumble in an automobile when the tires of the automobile impact a row of markers. The most commonly used permanent roadway marker is formed of ceramic and has a semi-hemispherical or button shape.
Temporary roadway markers serve to notify motorists that a construction area is near and that caution is needed. They often direct roadway traffic to pass along the portions of the roadway unaffected by construction, while protecting workers within a construction area from roadway traffic. After construction is completed, temporary roadway markers are loosened and removed. To be effective temporary roadway markers must alert traffic of the construction area. Typically, temporary roadway markers warn oncoming motorists by (1) the use of visual cues such as reflective surfaces, or (2) the use of physical cues such as causing a vehicle to rumble on contact with the marker. Both permanent and temporary roadway markers that provide visual cues often have a reflective surface that reflects light back to a driver. As noted above, physical cues are provided by a raised portion that causes the automobile to rumble upon contact with the marker. One example of a roadway marker that provides both visual and physical cues is described in U.S. Pat. No. 4,428,320, issued to Oplt et al. and entitled "Reflective Paving Marker." The Oplt et al. patent describes a roadway marker having a generally trapezoidal prism shape with a honeycombed interior, a reflective surface and raised areas. The honeycombed interior makes the marker lightweight, which is desirable. Although the roadway marker is lightweight, one disadvantage of the Oplt et al. roadway marker is its high manufacturing cost. Due to its construction, the Oplt et al. roadway marker must be injection molded. Injection molding is expensive when compared to other manufacturing processes such as extrusion. Many prior art roadway markers share these same disadvantages because they can only be formed by injection or some other molding processes.
The present invention provides lightweight, low-cost roadway markers that provide a physical rumbling cue and, in some versions, a visual (reflective) cue. Roadway markers formed in accordance with the present invention have a constant cross-sectional shape throughout their length, which allows them to be made by inexpensive extrusion manufacturing processes.